The present invention relates to a ruler which is movable step by step over a fixed distance and suitable for use with a scanner of a limited scanning width in reading data on a specified area of a document.
A small, inexpensive scanner has a narrow scanning width so that every time it reads a line, it must be shifted repeatedly over a distance corresponding to the scanning width to read the next line until it has scanned the entire data area. The conventional means so far provided for moving the scanner, step-by-step over a fixed distance is complicated in the construction as well as in the operation.